There are a variety of mattress types, distinguished in general by their construction. One particular type of mattress construction is generally referred to as a spring mattress. This type has a two dimensional matrix of resilient metal coils bound within a metal frame and covered with a pallet composed of several layers of materials. The coils resist compression, such as occurs when weight is applied to them, and thus could provide a firmer sleeping surface than other mattress construction types, if desired, such as foam mattresses.
A number of improvements have been made to the spring mattress, including varying the compressive strength of the individual coils in the matrix so that those which are likely to bear the greatest compressive loads have the most compressive strength. Springs with greater spring force are placed in that matrix where the load is expected to be greater, based on generalized assumptions about the load.
The material coverings that form the pallet have also improved. A spring mattress coil array could typically be covered by a thin mesh material to isolate the coils from the layers of materials above it. A thin fiber layer covers the mesh layer and then a thicker layer of foam is applied on top of the fiber layer. Finally, the mattress is finished with a quilted textile layer. The textile layer is bound to the balance of the mattress using a side wrap that covers the sides of the coil array and is sewn to quilted top and bottom panels.
Human beings spend one third of their lives in bed. Sleep is a vital part of human activity and essential for good health. It is believed that a mattress with support and good weight distribution provides a more restful sleep than one that is too soft and sinks in the middle. Therefore, mattress construction that improves comfortable firmness and weight distribution is a continuing objective of those who design mattresses.